Testing Helpers

Testing helpers follows previous patterns shown in Testing Components,
because helpers are rendered to templates just like components.

Helpers are best tested with integration tests, but can also be tested with unit
tests. Integration tests will provide better coverage for helpers, as it more
closely simulates the lifecycle of a helper than in isolation.

We're going to demonstrate how to test helpers by testing the format-currency
helper from Writing Helpers.

You can follow along by generating your own helper with ember generate helper
format-currency.